Alternator Problem?

[pleasecorrupt]

Long story short, battery progressively dying before Christmas, drove it all the way to norcal without turning off car to charge it back up (had to jump it to start). Battery seemed laggish for the time I was up there. Drove it back down and battery seemed to stay the same. Fast forward to today, bought a diehard battery @ sears, got a pre and post read on battery voltage, 11.7 with old battery, 12.1 with new battery but with both instances the alternator stayed around 13-13.4. According to stats found by this video
(http://www.youtube.com/watch?v=UGuMXU3SkLs) So do you guys think its actually my battery or is the alternator going out?

[kayger12]

My money is on the battery.

I wish this was sent with a Galaxy S3

[pleasecorrupt]

Already changed battery, so we'll see. Im just curious as to how the video poster got ~14.1 for the alternator while im only managing a measly 13-13.4 with the car on. New battery measured at 12.5 this past test so it's solid

[kayger12]

Sorry. I misunderstood about the battery being new.

I would just get the alternator bench tested.

That will tell the tale.

I wish this was sent with a Galaxy S3

[LivesNearCostco]

I think at idle my alternator is putting out <14v, somewhere in the 13.x range, as shown by the OBC display. Only when it's revving higher do I get up to 14.x volts.